1. Field of the Invention
The invention relates to a holder for an electrostatic high-voltage rod-shaped electrode, in particular an electrostatic high-voltage electrode and to an electrostatic fine dust filter system. The invention also relates to the use of specific materials for producing an electrode. The holder, electrode and/or fine dust filter system can be used for waste gas purification, in particular of fireplaces and hearths.
2. Prior Art
Electrostatic dust filters, also termed electrostatic precipitators, are systems for precipitating particles from gases, which act on the electrostatic principle. These systems are used in particular for the electrostatic purification of waste gases.
Electrostatic filters are mainly used in the purification of industrial flue gases, for example in generating electricity from coal, in smelting, or in cement production. There overall levels of precipitation of up to 99.9% are achieved. A power station filter is in some cases several tens of meters high. The precipitation of in particular toxic fine dusts in the range below one micrometre presents a particular challenge to the precipitation efficiency of electrostatic filters. Such dusts pass into the lungs and therefore cannot be expectorated. Depending on the particular substance, they represent a considerable cancer risk.
Fine dust fractions are however present not only in industrial waste gases, but also in domestic waste gases. In order also to purify these waste gases efficiently, nowadays electrostatic filter systems are installed in chimneys of private and commercial fireplaces and hearths. The installation, maintenance and cleaning of private and commercial fireplaces and hearths and their filter systems are subject to different requirements than large-scale industrial systems. In particular, ongoing industrial solutions for cleaning chimneys are very costly and are not financially feasible for private or commercial use of a fireplace or hearth; instead, in this case cleaning is carried out by chimney sweeps, for example annually. An electrostatic filter system for cleaning flue gases from small fireplaces and hearths that are fired with wood, straw or other regenerative fuels or coal is disclosed in patent specification DE 10 2006 003 028.
In the case of electrostatic filters, dust particles are electrically charged by corona discharge and are attracted to the oppositely charged electrode. The corona discharge takes place on a charged high-voltage electrode suitable for this purpose in the interior of the waste gas chimney. The electrode is designed having projecting tips and possibly sharp edges, since there the density of the field lines and thus also the electric field strength is greatest and therefore the corona discharge is promoted. The counter electrode usually consists of an earthed waste gas tubular section that is placed around the electrode. The precipitation efficiency of an electrostatic filter depends in particular on the residence time of the waste gases in the filter system and the voltage between the discharge electrode and the precipitation electrode. The rectified high voltage required for this purpose is supplied from a high-voltage generation unit. The high-voltage generation unit and the holder for the electrode have to be protected against dust and contamination in order to avoid undesired leakage currents and to prolong the service life of the system.
Known electrostatic filters are illustrated in patent specification GB 914 299. One embodiment of an electrostatic filter (FIG. 2), whose insulators are protected on account of structural measures against bending stresses and fracture, consist at least of a high-voltage part that rests on a carrier that forms a bridge between insulating supports. In addition the suspended high-voltage part extends through an insulator sleeve. Forces acting on the high-voltage part are absorbed by elastic seals, some of which rest directly or indirectly on the high-voltage part. The freedom of movement of the high-voltage part is almost completely prevented by the aforedescribed structure. In so far as a movement of the high-voltage part is possible at all, this is greatly restricted and guided by the adjoining seals. Vibrations and shocks can be damped by this structure.
In patent application GB 2 119 291 an electrostatic filter is illustrated, whose carrier rod, optionally with emission electrode, is freely suspended in an insulator sleeve. In one embodiment, the carrier rod is embedded in a flexible material that fills the space between the carrier rod and insulator. This structure is intended to prevent a fracture of the insulator on account of vibrations that are transmitted via the carrier rod.
In the patent application U.S. Pat. No. 4,671,808 an electrostatic filter with a tapping mechanism is shown. This tapping mechanism serves to shake the large number of electrodes. By actuating the tapping mechanism the precipitate is knocked off.
The publication WO 2008/128353 discloses a damper installation for separating the insulator chamber from the chimney pipe. If the damper installation is closed and the current supply to the holding element for the electrode frame is switched off, the maintenance of the insulator can be carried out while the waste gas continues to flow through the chimney.
The aforementioned prior art provides no details of the structural implementation of holders for electrostatic high-voltage electrodes of mainly small fireplaces and hearths, which are normally cleaned by chimney sweeps using brushes.
Thus, the present invention provides an electrostatic fine dust filter system, in particular an electrode and electrode holder, designed so that the installation, maintenance and cleaning of the fine dust filters and chimney, for example of wood-fired domestic chimneys, can be carried out easily. In particular the cleaning should be able to be carried out easily from the roof as well as from below, i.e. from the fireplace. In addition the safety of chimney sweeps and installers in the execution of the installation, service, maintenance and cleaning operations should be ensured.